I understand that the latest monero software already has all the RCT code. Does it mean that no upgrade will be required prior to RCT HF? If so, is the block height at which RCT will be allowed already hardcoded - at which block?
2 Answers
Does it mean that no upgrade will be required prior to RCT HF?
This is currently correct. However, Ring CT is also in a testing phase on testnet. Therefore, there exists a possibility that bugs are found that have to be fixed before the v4 fork enables Ring CT transactions on mainnet. If this happens, it would be wise to upgrade your software to the latest binaries before the v4 fork occurs.
If so, is the block height at which RCT will be allowed already hardcoded - at which block?
Yes it is, from the code:
// version 4 starts from block 1220517, which is on or around the 5th of January, 2017.
Does it mean that no upgrade will be required prior to RCT HF?
This was true until recently.
A problem was discovered with the initial version of RCT and it had been fixed in the point release 0.10.1. This means that everyone has to update the software to 0.10.1 prior to the HF date which is currently estimated to happen around 10-Jan-2017, and exactly at block 1220516.